Without any measurements of the drivers, can't really pass much in the way of comments, other than noting that a lot of trad. BR loads were generalised for maximum efficiency at Fb, & then needed a fair bit of empirical adjustment to dial in. You might give them a shot in the Chang cabinet itself; Vb isn't too far off the 1.5ft^3 box you say you have plans for, so it'll probably work as well in that as anything based on the available information.